add imp component to rad smem, add core serialized access, update 2p smem

2024-10-16 16:20:58 -07:00
parent 0989d90dd2
commit 9e86007e90
6 changed files with 225 additions and 92 deletions
--- a/src/main/scala/radiance/memory/SyncMem.scala
+++ b/src/main/scala/radiance/memory/SyncMem.scala
@@ -0,0 +1,81 @@
+package radiance.memory
+import chisel3._
+import chisel3.util._
+import midas.targetutils.SynthesizePrintf
+
+// modified from gemmini's two port sync mem
+class TwoPortSyncMem[T <: Data](n: Int, t: T, maskedUnitWidth: Int = 8) extends Module {
+  val maskWidth = t.getWidth / maskedUnitWidth
+  val io = IO(new Bundle {
+    val waddr = Input(UInt((log2Ceil(n) max 1).W))
+    val raddr = Input(UInt((log2Ceil(n) max 1).W))
+    val wdata = Input(t)
+    val rdata = Output(t)
+    val wen = Input(Bool())
+    val ren = Input(Bool())
+    val mask = Input(UInt(maskWidth.W))
+  })
+
+  when (io.wen && io.ren && io.raddr === io.waddr) {
+    SynthesizePrintf(printf("WARNING: read and write collided at address 0x%x\n", io.raddr))
+  }
+
+  val maskElem = UInt(maskedUnitWidth.W)
+  val memT = Vec(maskWidth, maskElem)
+  val mem = SyncReadMem(n, memT, SyncReadMem.WriteFirst)
+
+  io.rdata := mem.read(io.raddr, io.ren).asTypeOf(t)
+
+  when (io.wen) {
+    mem.write(io.waddr, io.wdata.asTypeOf(memT), io.mask.asBools)
+  }
+}
+
+class TwoReadOneWriteSyncMem[T <: Data](n: Int, t: T, maskedUnitWidth: Int = 8) extends Module {
+  val maskWidth = t.getWidth / maskedUnitWidth
+  val io = IO(new Bundle {
+    val waddr = Input(UInt((log2Ceil(n) max 1).W))
+    val raddr0 = Input(UInt((log2Ceil(n) max 1).W))
+    val raddr1 = Input(UInt((log2Ceil(n) max 1).W))
+    val wdata = Input(t)
+    val rdata0 = Output(t)
+    val rdata1 = Output(t)
+    val wen = Input(Bool())
+    val ren0 = Input(Bool())
+    val ren1 = Input(Bool())
+    val mask = Input(UInt(maskWidth.W))
+  })
+
+  when (io.wen && io.ren0 && io.raddr0 === io.waddr) {
+    SynthesizePrintf(printf("WARNING: read0 and write collided at address 0x%x\n", io.raddr0))
+  }
+  when (io.wen && io.ren1 && io.raddr1 === io.waddr) {
+    SynthesizePrintf(printf("WARNING: read1 and write collided at address 0x%x\n", io.raddr1))
+  }
+
+  val maskElem = UInt(maskedUnitWidth.W)
+  val memT = Vec(maskWidth, maskElem)
+  val mem0 = SyncReadMem(n, memT, SyncReadMem.WriteFirst)
+  val mem1 = SyncReadMem(n, memT, SyncReadMem.WriteFirst)
+
+  io.rdata0 := mem0.read(io.raddr0, io.ren0).asTypeOf(t)
+  io.rdata1 := mem1.read(io.raddr1, io.ren1).asTypeOf(t)
+
+  when (io.wen) {
+    mem0.write(io.waddr, io.wdata.asTypeOf(memT), io.mask.asBools)
+    mem1.write(io.waddr, io.wdata.asTypeOf(memT), io.mask.asBools)
+  }
+}
+
+
+object TwoPortSyncMem {
+  def apply[T <: Data](n: Int, t: T, maskedUnitWidth: Int = 8): TwoPortSyncMem[T] = {
+    Module(new TwoPortSyncMem[T](n, t, maskedUnitWidth))
+  }
+}
+
+object TwoReadOneWriteSyncMem {
+  def apply[T <: Data](n: Int, t: T, maskedUnitWidth: Int = 8): TwoReadOneWriteSyncMem[T] = {
+    Module(new TwoReadOneWriteSyncMem[T](n, t, maskedUnitWidth))
+  }
+}
--- a/src/main/scala/radiance/memory/XbarWithExtPolicy.scala
+++ b/src/main/scala/radiance/memory/XbarWithExtPolicy.scala
@@ -20,17 +20,22 @@ object ExtPolicyNodeImp extends SimpleNodeImp[Int, Int, Int, ExtPolicyBundle] {
 case class ExtPolicyMasterNode(w: Int)(implicit valName: ValName) extends SourceNode(ExtPolicyNodeImp)(Seq(w))
 case class ExtPolicySlaveNode()(implicit valName: ValName) extends SinkNode(ExtPolicyNodeImp)(Seq(0))

-class XbarWithExtPolicy(nameSuffix: Option[String] = None)
+class XbarWithExtPolicy(nameSuffix: Option[String] = None, useFallback: Boolean = true)
                       (implicit p: Parameters) extends TLXbar(nameSuffix = nameSuffix) {
  val policySlaveNode = ExtPolicySlaveNode()

  class ImplChild extends Impl {
    val policy: TLArbiter.Policy = (width, valids, select) => {
      val in = policySlaveNode.in.head._1
-      val hintHit = (valids & in.hint).orR
-      val fallback = TLArbiter.lowestIndexFirst(width, valids, !hintHit && select)
      in.actual := select.asTypeOf(in.actual.cloneType)
-      Mux(hintHit, in.hint, fallback)
+
+      if (useFallback) {
+        val hintHit = (valids & in.hint).orR
+        val fallback = TLArbiter.lowestIndexFirst(width, valids, !hintHit && select)
+        Mux(hintHit, in.hint, fallback)
+      } else {
+        in.hint
+      }
    }
    TLXbar.circuit(policy, node.in, node.out)
  }
@@ -44,4 +49,14 @@ object XbarWithExtPolicy {
    val xbar = LazyModule(new XbarWithExtPolicy(nameSuffix))
    xbar
  }
-}
+}
+
+object XbarWithExtPolicyNoFallback {
+  def apply(nameSuffix: Option[String] = None)
+           (implicit p: Parameters): (XbarWithExtPolicy, TLIdentityNode) = {
+    val inIdNode = TLIdentityNode()
+    val xbar = LazyModule(new XbarWithExtPolicy(nameSuffix, false))
+    xbar.node :=* inIdNode
+    (xbar, inIdNode)
+  }
+}
--- a/src/main/scala/radiance/subsystem/Configs.scala
+++ b/src/main/scala/radiance/subsystem/Configs.scala
@@ -15,6 +15,12 @@ import radiance.tile._
 import radiance.memory._
 import radiance.subsystem.RadianceGemminiDataType.{BF16, FP16, FP32, Int8}

+sealed trait RadianceSmemSerialization
+
+case object FullySerialized extends RadianceSmemSerialization
+case object CoreSerialized extends RadianceSmemSerialization
+case object NotSerialized extends RadianceSmemSerialization
+
 case class RadianceSharedMemKey(address: BigInt,
                                size: Int,
                                numBanks: Int,
@@ -23,7 +29,7 @@ case class RadianceSharedMemKey(address: BigInt,
                                strideByWord: Boolean = true,
                                filterAligned: Boolean = true,
                                disableMonitors: Boolean = true,
-                                serializeUnaligned: Boolean = true)
+                                serializeUnaligned: RadianceSmemSerialization = FullySerialized)
 case object RadianceSharedMemKey extends Field[Option[RadianceSharedMemKey]](None)

 case class RadianceFrameBufferKey(baseAddress: BigInt,
@@ -56,7 +62,7 @@ class WithRadianceCores(
        nTLBWays = 1,
        nTLBBasePageSectors = 1,
        nTLBSuperpages = 1,
-      nMSHRs = 0,
+        nMSHRs = 0,
        blockBytes = site(CacheBlockBytes))),
      icache = Some(ICacheParams(
        rowBits = site(SystemBusKey).beatBits,
@@ -194,8 +200,8 @@ class WithRadianceSharedMem(address: BigInt,
                            strideByWord: Boolean = true,
                            filterAligned: Boolean = true,
                            disableMonitors: Boolean = true,
-                            serializeUnaligned: Boolean = true
-                           ) extends Config((site, _, _) => {
+                            serializeUnaligned: RadianceSmemSerialization = FullySerialized
+                           ) extends Config((_, _, _) => {
  case RadianceSharedMemKey => {
    require(isPow2(size) && size >= 1024)
    Some(RadianceSharedMemKey(
--- a/src/main/scala/radiance/tile/RadianceCluster.scala
+++ b/src/main/scala/radiance/tile/RadianceCluster.scala
@@ -38,7 +38,9 @@ class RadianceCluster (

  // TODO: this probably needs to be instantiated inside the radiance shared mem module
  def virgoSharedMemComponentsGen() = new VirgoSharedMemComponents(thisClusterParams, gemminiTiles, radianceTiles)
-  LazyModule(new RadianceSharedMem(virgoSharedMemComponentsGen, clbus)).suggestName("shared_mem")
+  def virgoSharedMemComponentsImpGen(outer: VirgoSharedMemComponents) = new VirgoSharedMemComponentsImp(outer)
+  LazyModule(new RadianceSharedMem(
+    virgoSharedMemComponentsGen, Some(virgoSharedMemComponentsImpGen(_)), clbus)).suggestName("shared_mem")

  // direct core-accelerator connections
  val smemKey = p(RadianceSharedMemKey).get
--- a/src/main/scala/radiance/tile/RadianceSharedMem.scala
+++ b/src/main/scala/radiance/tile/RadianceSharedMem.scala
@@ -4,14 +4,14 @@ import chisel3._
 import chisel3.util._
 import org.chipsalliance.diplomacy.lazymodule._
 import org.chipsalliance.cde.config.Parameters
-import radiance.memory._
 import freechips.rocketchip.tilelink._
 import freechips.rocketchip.diplomacy.{AddressSet, TransferSizes}
+import gemmini.Pipeline
 import radiance.subsystem.RadianceSharedMemKey
-import gemmini._
+import radiance.memory._
 import scala.collection.mutable.ArrayBuffer

-trait RadianceSmemNodeProvider {
+abstract class RadianceSmemNodeProvider {
  val uniformRNodes: Seq[Seq[Seq[TLNexusNode]]]
  val uniformWNodes: Seq[Seq[Seq[TLNexusNode]]]
  val nonuniformRNodes: Seq[TLNode]
@@ -19,8 +19,11 @@ trait RadianceSmemNodeProvider {
  val clBusClients: Seq[TLNode]
 }

-class RadianceSharedMem(
-    provider: () => RadianceSmemNodeProvider,
+abstract class RadianceSmemNodeProviderImp[T <: RadianceSmemNodeProvider](val outer: T) {}
+
+class RadianceSharedMem[T <: RadianceSmemNodeProvider](
+    provider: () => T,
+    val providerImp: Option[(T) => RadianceSmemNodeProviderImp[T]],
    clbus: TLBusWrapper
  )(implicit p: Parameters) extends LazyModule {
  val smemKey = p(RadianceSharedMemKey).get
@@ -31,6 +34,7 @@ class RadianceSharedMem(
  val smemDepth = smemKey.size / smemWidth / smemBanks
  val smemSubbanks = smemWidth / wordSize
  val smemSize = smemWidth * smemDepth * smemBanks
+  val strideByWord = smemKey.strideByWord

  require(isPow2(smemBanks))

@@ -38,11 +42,7 @@ class RadianceSharedMem(
  val (uniformRNodes, uniformWNodes, nonuniformRNodes, nonuniformWNodes) =
    (smNodes.uniformRNodes, smNodes.uniformWNodes, smNodes.nonuniformRNodes, smNodes.nonuniformWNodes)

-  // TODO: move this to config
-  val strideByWord = true
-  val filterAligned = true
-  val serializeUnaligned = true
-  implicit val disableMonitors = true // otherwise it generate 1k+ different tl monitors
+  implicit val disableMonitors = smemKey.disableMonitors // otherwise it generate 1k+ different tl monitors

  // collection of read and write managers for each sram (sub)bank
  val smemBankMgrs : Seq[Seq[TLManagerNode]] = if (strideByWord) {
@@ -180,9 +180,11 @@ class RadianceSharedMem(
  lazy val module = new RadianceSharedMemImp(this)
 }

-class RadianceSharedMemImp(outer: RadianceSharedMem) extends LazyModuleImp(outer) {
+class RadianceSharedMemImp[T <: RadianceSmemNodeProvider](outer: RadianceSharedMem[T]) extends LazyModuleImp(outer) {

-  def makeBuffer[T <: Data](mem: TwoPortSyncMem[T], rNode: TLBundle, rEdge: TLEdgeIn,
+  val smNodesImp = outer.providerImp.map(impFn => impFn(outer.smNodes))
+
+  def makeBuffer[U <: Data](mem: TwoPortSyncMem[U], rNode: TLBundle, rEdge: TLEdgeIn,
                            wNode: TLBundle, wEdge: TLEdgeIn): Unit = {
    mem.io.ren := rNode.a.fire

@@ -240,7 +242,7 @@ class RadianceSharedMemImp(outer: RadianceSharedMem) extends LazyModuleImp(outer
    // WRITE
    mem.io.wen := RegNext(wNode.a.fire)
    mem.io.wdata := RegNext(wNode.a.bits.data)
-    mem.io.mask := RegNext(VecInit(wNode.a.bits.mask.asBools))
+    mem.io.mask := RegNext(wNode.a.bits.mask)

    val writeResp = Wire(Flipped(wNode.d.cloneType))
    writeResp.bits := wEdge.AccessAck(wNode.a.bits)
@@ -286,7 +288,6 @@ class RadianceSharedMemImp(outer: RadianceSharedMem) extends LazyModuleImp(outer
        val mem = TwoPortSyncMem(
          n = memDepth,
          t = UInt((wordWidth * 8).W),
-          mask_len = wordWidth // byte level mask
        )
        // TODO: bring in cluster id
        // mem.suggestName(s"rad_smem_cl${outer.thisClusterParams.clusterId}_b${bid}_w${wid}")
@@ -346,7 +347,6 @@ class RadianceSharedMemImp(outer: RadianceSharedMem) extends LazyModuleImp(outer
      val mem = TwoPortSyncMem(
        n = memDepth,
        t = UInt((memWidth * 8).W),
-        mask_len = memWidth // byte level mask
      )

      val (rNode, rEdge) = r.in.head
--- a/src/main/scala/radiance/tile/VirgoSharedMemComponents.scala
+++ b/src/main/scala/radiance/tile/VirgoSharedMemComponents.scala
@@ -9,8 +9,9 @@ import radiance.memory._
 import freechips.rocketchip.tilelink._
 import freechips.rocketchip.diplomacy.{AddressSet, BufferParams}
 import freechips.rocketchip.subsystem.BaseClusterParams
-import radiance.subsystem.RadianceSharedMemKey
+import radiance.subsystem.{CoreSerialized, FullySerialized, NotSerialized, RadianceSharedMemKey}
 import gemmini._
+import scala.collection.mutable.ArrayBuffer

 // virgo-specific tilelink nodes
 // generic smem implementation is in RadianceSharedMem.scala
@@ -28,6 +29,9 @@ class VirgoSharedMemComponents(
  val smemSubbanks = smemWidth / wordSize
  val smemSize = smemWidth * smemDepth * smemBanks

+  val numCores = radianceTiles.length
+  val numLanes = radianceTiles.head.numLsuLanes
+
  val gemminis = gemminiTiles.map(_.gemmini)
  val gemminiConfigs = gemminis.map(_.config)
  gemminiConfigs.foreach { config =>
@@ -55,11 +59,25 @@ class VirgoSharedMemComponents(
    }
  }
  val tcNodeFanouts = radianceTiles.flatMap(_.tcSmemNodes)
-    .map(connectOne(_, () => TLBuffer(BufferParams(2, false, false), BufferParams(0))))
+    // .map(connectOne(_, () => TLBuffer(BufferParams(2, false, false), BufferParams(0))))
    .map(connectXbarName(_, Some("tc_fanout")))
  val clBusClients: Seq[TLNode] = radianceSmemFanout

-  val (uniformRNodes, uniformWNodes, nonuniformRNodes, nonuniformWNodes) =
+  // convert to monad (very fancy)
+  val coreSerialOpt: Option[Unit] = serializeUnaligned match {
+    case CoreSerialized => Some(())
+    case _ => None
+  }
+
+  // uniform mux select for selecting lanes from a single core in unison
+  val coreSerialPolicy = coreSerialOpt.map(_ => Seq.fill(2)(Seq.fill(numLanes)(ExtPolicyMasterNode(numCores))))
+  val laneSerialXbars = coreSerialOpt.map(_ => Seq.tabulate(2) { rw =>
+    Seq.tabulate(numLanes) { lid =>
+      XbarWithExtPolicyNoFallback(Some(f"lane_${lid}_serial_in_xbar_$rw"))
+    }
+  })
+
+  override val (uniformRNodes, uniformWNodes, nonuniformRNodes, nonuniformWNodes) =

  if (strideByWord) {
    def distAndDuplicate(nodes: Seq[TLNode], suffix: String): Seq[Seq[TLNexusNode]] = {
@@ -93,57 +111,35 @@ class VirgoSharedMemComponents(
      Seq.fill(smemSubbanks)(tcBank.map(connectOne(_, () => TLBuffer(BufferParams(2, false, false)))).map(connectXbarName(_, Some("tc_dist_fanout"))))
    } // (banks, subbanks, tc client)

+    val unalignedRWNodes: ArrayBuffer[ArrayBuffer[TLNexusNode]] = // mutable for readability
+      ArrayBuffer.fill(numLanes)(ArrayBuffer.fill(numCores)(null))
+
    if (filterAligned) {
-      val numLsuLanes = radianceTiles.head.numLsuLanes
-      val numLaneDupes = Math.max(1, smemSubbanks / numLsuLanes)
-      val filterRange = Math.min(smemSubbanks, numLsuLanes)
-      println(s"num_lsu_lanes ${numLsuLanes} num_lane_dupes ${numLaneDupes} filter_range ${filterRange}")
+      val numLaneDupes = Math.max(1, smemSubbanks / numLanes)
+      val filterRange = Math.min(smemSubbanks, numLanes)

-      // (subbank, sources, aligned) = rw node
-      val (fAligned, fUnaligned) = if (numLsuLanes >= smemSubbanks) {
-        val filterNodes: Seq[Seq[(TLNode, TLNode)]] = Seq.tabulate(numLaneDupes) { did =>
-          Seq.tabulate(filterRange) { wid =>
-            val trueWid = did * filterRange + wid
-            val address = AddressSet(smemBase + wordSize * trueWid, (smemSize - 1) - (smemSubbanks - 1) * wordSize)
+      // (subbank, sources) = rw node
+      val fAligned = if (numLanes >= smemSubbanks) {
+        val filterNodes: Seq[Seq[TLNode]] = Seq.tabulate(filterRange) { wid =>
+          val address = AddressSet(smemBase + wordSize * wid, (smemSize - 1) - (smemSubbanks - 1) * wordSize)

-            radianceSmemFanout.grouped(numLsuLanes).toList.zipWithIndex.flatMap { case (lanes, cid) =>
-              lanes.zipWithIndex.flatMap { case (lane, lid) =>
-                if ((lid % filterRange) == wid) {
-                  println(f"c${cid}_l${lid} connected to d${did}w${wid}")
-                  val filterNode = AlignFilterNode(Seq(address))(p, ValName(s"filter_l${lid}_w${trueWid}"))
-                  DisableMonitors { implicit p => filterNode := lane }
-                  // Seq((aligned splitter, unaligned splitter))
-                  Seq((
-                    connectOne(filterNode, () =>
-                      RWSplitterNode(address, s"aligned_splitter_c${cid}_l${lid}_w${trueWid}")),
-                    connectOne(filterNode, () =>
-                      RWSplitterNode(AddressSet.everything, s"unaligned_splitter_c${cid}_l${lid}"))
-                  ))
-                } else Seq()
-              }
+          radianceSmemFanout.grouped(numLanes).toList.zipWithIndex.flatMap { case (lanes, cid) =>
+            lanes.zipWithIndex.flatMap { case (lane, lid) =>
+              if ((lid % filterRange) == wid) {
+                val filterNode = AlignFilterNode(Seq(address))(p, ValName(s"filter_l${lid}_w${wid}"))
+                DisableMonitors { implicit p => filterNode := lane }
+
+                unalignedRWNodes(lid)(cid) = connectOne(filterNode, () =>
+                  RWSplitterNode(AddressSet.everything, s"unaligned_splitter_c${cid}_l${lid}"))
+
+                Seq(connectOne(filterNode, () =>
+                  RWSplitterNode(address, s"aligned_splitter_c${cid}_l${lid}_w${wid}")))
+              } else Seq()
            }
          }
-        }.flatten
-
-        val fAligned = Seq.fill(2)(filterNodes.map(_.map(_._1).map(connectXbarName(_, Some("rad_aligned")))))
-        val fUnaligned = if (serializeUnaligned) {
-          Seq.fill(2) {
-            val serializedNode = TLEphemeralNode()
-            val serializedInXbar = LazyModule(new TLXbar())
-            val serializedOutXbar = LazyModule(new TLXbar())
-            serializedInXbar.suggestName("unaligned_serialized_in_xbar")
-            serializedOutXbar.suggestName("unaligned_serialized_out_xbar")
-            guardMonitors { implicit p =>
-              filterNodes.foreach(_.map(_._2).foreach(serializedInXbar.node := _))
-              serializedNode := serializedInXbar.node
-              serializedOutXbar.node := serializedNode
-            }
-            Seq(serializedOutXbar.node)
-          }
-        } else {
-          Seq.fill(2)(filterNodes.flatMap(_.map(_._2).map(connectXbar.apply)))
        }
-        (fAligned, fUnaligned)
+
+        Seq.fill(2)(filterNodes.map(_.map(connectXbarName(_, Some("rad_aligned")))))
      } else { // aligned: (subbanks, cores) = rw node
        // (lanes, cores) = filter_node
        val filterNodes = Seq.tabulate(filterRange) { wid =>
@@ -151,7 +147,7 @@ class VirgoSharedMemComponents(
            AddressSet(smemBase + (did * filterRange + wid) * wordSize,
              (smemSize - 1) - (smemSubbanks - 1) * wordSize)
          }
-          radianceSmemFanout.grouped(numLsuLanes).toSeq.zipWithIndex.map { case (lanes, cid) =>
+          radianceSmemFanout.grouped(numLanes).toSeq.zipWithIndex.map { case (lanes, cid) =>
            val lane = lanes(wid)
            val filterNode = AlignFilterNode(addresses)(p, ValName(s"filter_c${cid}_w${wid}"))
            guardMonitors { implicit p =>
@@ -169,29 +165,40 @@ class VirgoSharedMemComponents(
            }
          }
        }.flatten
-        val fUnalignedRW = filterNodes.zipWithIndex.flatMap { case (cores, lid) =>
-          cores.zipWithIndex.map { case (fn, cid) =>
-            connectOne(fn, () => RWSplitterNode(AddressSet.everything, s"unaligned_split_c${cid}_l${lid}"))
+        filterNodes.zipWithIndex.foreach { case (cores, lid) =>
+          cores.zipWithIndex.foreach { case (fn, cid) =>
+            unalignedRWNodes(lid)(cid) = connectOne(fn, () =>
+              RWSplitterNode(AddressSet.everything, s"unaligned_split_c${cid}_l${lid}"))
          }
        }
-        val fAligned = Seq.fill(2)(fAlignedRW.map(_.map(connectXbarName(_, Some("rad_aligned")))))
+        Seq.fill(2)(fAlignedRW.map(_.map(connectXbarName(_, Some("rad_aligned")))))
+      }

-        val fUnaligned = if (serializeUnaligned) {
-          Seq.fill(2) {
-            val serializedNode = TLEphemeralNode()
-            val serializedInXbar = TLXbar(nameSuffix = Some("unaligned_ser_in"))
-            val serializedOutXbar = TLXbar(nameSuffix = Some("unaligned_ser_out"))
-            guardMonitors { implicit p =>
-              fUnalignedRW.foreach(serializedInXbar := _)
-              serializedNode := serializedInXbar
-              serializedOutXbar := serializedNode
-            }
-            Seq(serializedOutXbar)
+      val fUnaligned: Seq[Seq[TLNode]] = serializeUnaligned match {
+        case FullySerialized => Seq.fill(2) {
+          val serializedNode = TLEphemeralNode()
+          val serializedInXbar = LazyModule(new TLXbar())
+          val serializedOutXbar = LazyModule(new TLXbar())
+          serializedInXbar.suggestName("unaligned_serialized_in_xbar")
+          serializedOutXbar.suggestName("unaligned_serialized_out_xbar")
+          guardMonitors { implicit p =>
+            unalignedRWNodes.flatten.foreach(serializedInXbar.node := _)
+            serializedNode := serializedInXbar.node
+            serializedOutXbar.node := serializedNode
          }
-        } else {
-          Seq.fill(2)(fUnalignedRW.map(connectXbar.apply))
+          Seq(serializedOutXbar.node)
        }
-        (fAligned, fUnaligned)
+        case CoreSerialized => Seq.tabulate(2) { rw =>
+          // we can either have one core per lane selected (multiple mux selects)
+          // or strictly lanes from a single selected core (one mux select). doing the latter here
+          unalignedRWNodes.toSeq.zipWithIndex.map { case (coresRW, lid) =>
+            val laneSerialXbar = laneSerialXbars.get(rw)(lid)
+            laneSerialXbar._1.policySlaveNode := coreSerialPolicy.get(rw)(lid)
+            coresRW.foreach(laneSerialXbar._2 := _)
+            connectXbarName(connectOne(laneSerialXbar._1.node, TLEphemeralNode.apply), Some(s"lane_${lid}_serial_out"))
+          }
+        }
+        case NotSerialized => Seq.fill(2)(unalignedRWNodes.toSeq.flatten.map(connectXbar.apply))
      }


@@ -215,6 +222,8 @@ class VirgoSharedMemComponents(
      val uniformWNodes: Seq[Seq[Seq[TLNexusNode]]] = (spadWriteNodes zip spadSpWriteNodes).map { case (wb, wsb) =>
        (wb zip wsb).map { case (ww, wsw) => ww ++ wsw }
      }
+      // random accesses are not serialized here, require so
+      require(serializeUnaligned == NotSerialized, "when not filtering, unaligned accesses must be serialized")
      // these nodes are random access
      val nonuniformRNodes: Seq[TLNode] = splitterNodes.map(connectXbarName(_, Some("rad_unaligned_r")))
      val nonuniformWNodes: Seq[TLNode] = splitterNodes.map(connectXbarName(_, Some("rad_unaligned_w")))
@@ -242,3 +251,23 @@ class VirgoSharedMemComponents(
    (Seq.empty, Seq.empty, Seq(unifiedMemReadNode), Seq(unifiedMemWriteNode))
  }
 }
+
+class VirgoSharedMemComponentsImp[T <: VirgoSharedMemComponents]
+  (override val outer: T) extends RadianceSmemNodeProviderImp[T](outer) {
+
+  (outer.laneSerialXbars zip outer.coreSerialPolicy).foreach { case (xbarsRW, policiesRW) =>
+    (xbarsRW zip policiesRW).foreach { case (xbars, policies) =>
+      // for each lane, if any core is valid
+      val coreValids = xbars.map(_._2.in.map(_._1)).transpose.map { core => VecInit(core.map(_.a.valid)).asUInt.orR }
+      val select = xbars.map(_._2.out.map(_._1)).transpose.map { core => VecInit(core.map(_.a.ready)).asUInt.orR }
+      val coreSelect = TLArbiter.roundRobin(outer.numCores, VecInit(coreValids).asUInt, VecInit(select).asUInt.orR)
+      // TODO: roll this into XbarWithExtPolicy
+      xbars.foreach { lane =>
+        (lane._2.in.map(_._1) lazyZip lane._2.out.map(_._1) lazyZip coreSelect.asBools).foreach { case (li, lo, cs) =>
+          lo.a.valid := li.a.valid && cs
+        }
+      }
+      policies.foreach { _.out.head._1.hint := coreSelect }
+    }
+  }
+}